title: Structural kinetics of a Pt/C cathode catalyst with practical catalyst loading in an MEA for PEFC operating conditions studied by in situ time-resolved XAFS.
abstract: The structural kinetics of surface events on a Pt/C cathode catalyst in a membrane electrode assembly (MEA) with a practical catalyst loading (0.5 mgPt cm(-2)) for a polymer electrolyte fuel cell were investigated by in situ time-resolved X-ray absorption fine structure analysis (XAFS; time resolution: 100 ms) for the first time. The rate constants of structural changes in the Pt/C cathode catalyst in the MEA during voltage cycling were successfully estimated. For voltage-cycling processes, all reactions (electrochemical reactions and structural changes in the Pt catalyst) in the MEA were found to be much faster than those in an MEA with a thick cathode catalyst layer, but the in situ time-resolved XAFS analysis revealed that significant time lags similarly existed between the electrochemical reactions and the structural changes in the Pt cathode catalyst. The time-resolved XAFS also revealed differences in the structural kinetics of the Pt/C cathode catalyst for the voltage-cycling processes under N2 and air flows at the cathode.
authors.affiliation: Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki, Aichi 444-8585, Japan.
authors.forename: Nozomu
authors.initials: N
authors.lastname: Ishiguro
authors.forename: Takahiro
authors.initials: T
authors.lastname: Saida
authors.forename: Tomoya
authors.initials: T
authors.lastname: Uruga
authors.forename: Oki
authors.initials: O
authors.lastname: Sekizawa
authors.forename: Kensaku
authors.initials: K
authors.lastname: Nagasawa
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Nitta
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ohkoshi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Mizuki
authors.initials: M
authors.lastname: Tada